Phased Array Ultrasonic Testing Research Articles

Phased array ultrasonic S-scan testing of near-detection-surface defects based on a background subtraction algorithm

In phased array ultrasonic sector scanning testing, echoes from defects near the detection surface are often overlapped with interface echoes and cannot be characterized. Based on linear acoustic theory, a mathematical model combining the background subtraction and the sum of squares differences algorithm is established to extract the characteristics of near-detection-surface defect echoes. The upper surface of the artificial notch defect is used as a near-detection-surface defect for detection. Specially, linear interpolation algorithm is used to suppress the effect of residual interface echo on the defect echo feature extraction and the effect of different interpolation factors is analyzed. The defect location and size were calculated based on the extracted defect characteristics. The simulation and experimental results indicate that the model can effectively extract the near-detection-surface defect echoes characteristics. Furthermore, when the interpolated signal reaches at least 500 MHz, residual interface echoes can be effectively suppressed. More importantly, according to the extracted defect echo characteristics, the localization and quantitative accuracies of near-surface defects can reach 0.2 mm and 0.3 mm, respectively. These findings provide an effective strategy for phased array ultrasonic sector scanning testing of near-detection-surface defects.

Electron Beam Welding Process of Port Stub of CFETR Vacuum Vessel Sector Mockup

Port structures are important parts of vacuum vessel (VV) in China Fusion Engineer Test Reactor (CFETR), which consists of port stubs and port extensions, mainly provides channels for the installation and maintenance of internal components, such as divertor and blanket, and provides interface for auxiliary heating system, diagnostic system, and vacuum pumping. A 1/8 VV sector mockup with port structures is used to explore the key manufacturing technology of CFETR VV. Electron beam welding (EBW) process development of port structures of 1/8 VV sector mockup is introduced in this article taking the inner shell of upper port stub as an example. Through EBW test and process optimization, the surface formation, microstructure, and mechanical properties of the weld are obtained. On this basis, the EBW of the inner shell of the upper port stub is carried out. After phased array ultrasonic nondestructive testing and laser tracker measurement, the weld quality is excellent, and contour accuracy has reached the technical requirements. This study provides important support for the engineering design and construction of the CFETR.

RETRACTED: Phased array ultrasonic test signal enhancement and classification using Empirical Wavelet Transform and Deep Convolution Neural Network

In the recent past, Non-Destructive Testing (NDT) has become the most popular technique due to its efficiency and accuracy without destroying the object and maintaining its original structure and gathering while examining external and internal welding defects. Generally, the NDT environment is harmful which is distinguished by huge volatile fields of electromagnetic, elevated radiation emission instability, and elevated heat. Therefore, a suitable NDT approach could be recognized and practiced. In this paper, a novel algorithm is proposed based on a Phased array ultrasonic test (PAUT) for NDT to attain the proper test attributes. In the proposed methodology, the carbon steel welding section is synthetically produced with various defects and tested using the PAUT method. The signals which are acquired from the PAUT device are having noise. The Adaptive Least Mean Square (ALMS) filter is proposed to filter PAUT signal to eliminate random noise and Gaussian noise. The ALMS filter is the combination of low pass filter (LPF), high pass filter (HPF), and bandpass filter (BPF). The time-domain PAUT signal is converted into a frequency-domain signal to extract more features by applying the Empirical Wavelet Transform (EWT) algorithm. In the frequency domain signal, first order and second order features extraction techniques are applied to extract various features for further classification. The Deep Learning methodology is proposed for the classification of PAUT signals. Based on the PAUT signal features, the Deep Convolution Neural Network (DCNN) is applied for further classification. The DCNN will classify the welding signal as to whether it is defective or non-defective. The Confusion Matrix (CM) is used for the estimation of measurement of performance of classification as calculating accuracy, sensitivity, and specificity. The experiments prove that the proposed methodology for PAUT testing for welding defect classification is obtained more accurately and efficiently across existing methodologies by providing numerical and graphical results.

Containment Liner Plate Void Defect Detection Technique Using Phased Array Ultrasonic Testing and Acoustic Resonance Method.

The CLP (containment liner plate) of a nuclear power plant protects the internal system from the external environment and sudden changes in internal pressure or temperature, and it is a structure that blocks and protects radioactive materials leaking inside and outside in the event of a nuclear accident and is composed of a liner plate, reinforcing bars, tendons, and concrete. Recently, corrosion on the rear side of the liner plate and concrete voids has emerged as a severe defect in nuclear power plants across South Korea. Therefore, in this study, we proposed a new inspection method that a line-type inspection method applied phased array ultrasonic testing and the area inspection method applied acoustic resonance method using developed moveable tapper. The acoustic signals were signal-processed and reproduced to a mapping image following the inspection area, and with the image, it was possible to determine the type of defect. Furthermore, an automated inspection system for within the CLP was proposed.

Dual Matrix Array Probe Based Phased Array Ultrasonic Testing for Inspection of Trimetallic Weld Joints

Dual Matrix Array Probe Based Phased Array Ultrasonic Testing for Inspection of Trimetallic Weld Joints

Influence of water and defects on abnormal temperature rise of composite insulator

Water and defects of composite insulator may cause its abnormal temperature rise, which seriously affects the safety of power grid. In this paper, the temperature rise tests of a 110 kV composite insulator before, after water immersion, and after water immersion and drying are firstly carried out. Then a phased array ultrasonic detector is used to detect the internal defects of the insulator. And the phased array ultrasonic recognition model for internal defects is proposed. Finally, the transverse anatomical test is carried out to verify the defects of composite insulator obtained by the temperature rise test and the phased array ultrasonic testing test. The results show that the temperature rise of composite insulator after water immersion is higher than that before water immersion. The maximum temperature rise of the insulator after water immersion is 1.2℃. And there is no temperature rise after drying. The defect between the sheath and the core rod at the temperature rise position after immersion is detected by the phased array ultrasonic testing. Cracks and discharge defects are observed anatomically. The accuracy of identification model is proved. And it provides an effective method for nondestructive detection of internal defects of composite insulator in the laboratory. According to the results of temperature rise test, ultrasonic detection and anatomical test, the high water content of the composite insulator sheath is one of the reasons for the slight temperature rise of the insulator. And water and defects are the direct reasons for the obvious temperature rise of composite insulator.

Ultrasonic Inspection for Welds with Irregular Curvature Geometry Using Flexible Phased Array Probes and Semi-Auto Scanners: A Feasibility Study

Pipes of various shapes constitute pipelines utilized in industrial sites. These pipes are coupled through welding, wherein complex curvatures such as a flange, an elbow, a reducer, and a branch pipe are often found. Using phased array ultrasonic testing (PAUT) to inspect weld zones with complex curvatures is faced with different challenges due to parts that are difficult to contact with probes, small-diameter pipes, spatial limitations due to adjacent pipes, nozzles, and sloped shapes. In this study, we developed a flexible PAUT probe (FPAPr) and a semi-automatic scanner that was improved to enable stable FPAPr scanning for securing its inspection data consistency and reproducibility. A mock-up test specimen was created for a flange, an elbow, a reducer, and a branch pipe. Artificial flaws were inserted into the specimen through notch and hole processing, and simulations and verification experiments were performed to verify the performance and field applicability of the FPAPr and semi-automatic scanner.

Research on 3D Defect Reconstruction in Plate with Phased Array Ultrasonic Test (PAUT)

In order to clarify the distribution and shape information of the defects inside the workpiece, it has become a new industrial testing requirement to display the defects more intuitively in three dimensions(3D). In this paper, by introducing 3D volume rendering method, the expansion of PAUT from 2D to 3D is realized. The method is used to reconstruct specific “gu-shaped [[CHECK_DOUBLEQUOT_ENT]] (“Gu” is the Pinyin in Chinese characters, and at the same time, “Gu” is the shape of the defect in the plate discussed in the paper.) defects, and the results of reconstruction are compared with actual defects. By using ultrasonic phased array focusing to detect defect C-scan images of different depths, the collected C-scan images were preprocessed and reconstructed according to the defect contour by volume rendering. The results show that the defect morphology with different depths can be well obtained by focused detection, and the reconstruction effect is good, which is consistent with the actual defect.

Application of advanced NDT methods to assess structural integrity of pressure vessel welded joints

The review of non-destructive testing of pressure vessel for compressed air is given, as well as the assessment and analysis of defects on the integrity of the vessel itself. The focus here is on welded joints, as the most critical areas in pressure vessels, especially if thickness is large, like in the case considered here (50 mm), cylindrical air storage vessels made of HSLA steel. Toward this end conventional NDT methods, such as UT and Radiography are used in the first phase of this research, providing valuable data for structural integrity assessment based on detected unacceptable defects in welded joints. Anyhow, since few unacceptable defects were found by conventional UT, there was a need to use advanced NDT UT methods, such as Phased Array Ultrasonic Testing (PAUT), to evaluate defect position and size more precisely. In this way risk of failure can be assessed more reliable, which is of utmost importance for pressure vessel where probability of failure is low, but the consequence of failure is potentially catastrophic, like in the case considered here.

High frequency phased array ultrasonic testing of thermoplastic tensile specimens manufactured by fused filament fabrication with embedded defects

Fused filament fabrication (FFF) is a popular additive manufacturing process used for fabrication of polymeric components. In this paper, defects are intentionally designed and induced in FFF 3D printed tensile specimens made from polylactic acid (PLA) per ASTM D638-14. Each fabricated sample consists of 24 layers and has a quasi-isotropic layup of [45/0/90/–45]3s. The defects (gaps) are in the form of 5, 7, 9 and 11 adjacent missing extrudates in the 10th layer, which has a 0° raster angle. Five specimens per each gap width, including no gap as the baseline, are 3D printed for a total of 25 specimens. The specimens are first scanned by high-frequency phased array ultrasonic testing (PAUT) and their layups are then accurately captured. This is the first time such high-resolution images are prepared from individual layers of 3D printed parts fabricated by FFF process. The as-manufactured gap widths are found to be within 10% of the as-designed values and are generally smaller. Next, the specimens are subjected to destructive tensile testing and their tensile properties are compared to the baseline. The relationship between the gap width and tensile properties of the specimens supports the suitability of high frequency PAUT for non-destructive testing of 3D printed parts.

Laboratory Study on Non-Destructive Evaluation of Polyethylene Liquid Storage Tanks by Thermographic and Ultrasonic Methods

High-density polyethylene (HDPE) above-ground storage tanks (AST) are used by highway agencies to store liquid deicing chemicals for the purpose of road maintenance in the winter. A sudden AST failure can cause significant economic and environmental impacts. While ASTs are routinely inspected to identify signs of aging and damage, current methods may not adequately capture all defects, particularly if they are subsurface or too small to be seen during visual inspection. Therefore, to improve the ability to identify potential durability issues with HDPE ASTs, additional non-destructive evaluation (NDE) techniques need to be considered and assessed for applicability. Specifically, this study investigates the efficiency of using infrared thermography (IRT) as a rapid method to simultaneously examine large areas of the tank exterior, which will be followed by closer inspections with conventional and phased array ultrasonic testing (UT) methods. Results show that IRT can help to detect defects that are shallow, specifically located within half of the tank’s wall thickness from the surface. UT has the ability to detect all defects at any depth. Moreover, phased array UT helps to identify stacked defects and characterize each defect more precisely than IRT.

Probability of detection of discontinuities by ultrasonic phased array inspection of 9% Ni steel joints welded with alloy 625 as the filler metal

For the first time, the 9% Ni steel is being used in CO2 injection units in floating production storage offloading vessels. Pipe joints welded with nickel-based superalloy 625 as the filler metal present difficulties in ultrasonic inspection owing to the sonic attenuation and deviation caused by the anisotropic and coarse-grained weld metal. This study aims to conduct a probability of detection (POD) to evaluate the discontinuity detection reliability in 9% Ni steel arc welded joints. The inspections were performed using ultrasonic phased array transducers with transversal and longitudinal waves, by using both a conventional wedge formed of Rexolite® and an adapted wedge filled with water to simulate the immersion inspection. POD curves were developed using the hit/miss and â vs a models. The inspection performed with transversal waves detected much fewer discontinuities than that performed with longitudinal waves. Furthermore, inspection performed with longitudinal waves after weld metal cap pass removal exhibited much more reliability in 9% Ni steel welded joints. The obtained POD curves were shown to be a suitable tool to evaluate the inspection of 9% Ni steel welded joints, as they confirmed that the best inspection procedure involves a combination of three different phased array ultrasonic testing configurations.

Optimizing Probe Active Aperture for Phased Array Weld Inspections

Phased array ultrasonic testing (PAUT) has become a popular nondestructive technique for weld inspections in piping, pressure vessels, and other components such as turbines. This technique can be used both in manual and automated modes. PAUT is more attractive than conventional angle-beam ultrasonic testing (UT), as it sweeps the beam through a range of angles and presents a cross-sectional image of the area of interest. Other displays are also available depending on the software. Unlike traditional A-scan instruments, which require the reconstruction of B- and C-scan images from raster scanning, a phased array image is much simpler to produce from line scans and easier to interpret. Engineering codes have incorporated phased array technology and provide steps for standardization, scanning, and alternate acceptance criteria based on fracture mechanics. The basis of fracture mechanics is accurate defect sizing. There is, however, no guidance in codes and standards on the selection and setup of phased array probes for accurate sizing. Just like conventional probes, phased array probes have a beam spread that depends on the probe’s active aperture and frequency. Smaller phased array probes, when used for thicker sections, result in poor focusing, large beam spread, and poor discontinuity definition. This means low resolution and oversizing. Accurate sizing for fracture mechanics acceptance criteria requires probes with high resolution. In this paper, guidance is provided for the selection of phased array probes and setup parameters to improve resolution, definition, and sizing of discontinuities.

Power Plant Small-diameter Tube Phased Array Inspection Verification and Inspection Technology

In this paper, the phased array inspection is carried out on the small diameter pipes with artificial groove defects and natural defects, and then the conventional ultrasonic inspection and the penetration inspection after cutting and dissection are carried out respectively. The ultrasonic phased array inspection results are compared with the conventional ultrasonic and compared with the results obtained from penetrant testing, the reliability of ultrasonic phased array testing technology in the application of small-diameter pipe testing is analyzed. Then, taking the detection of the small pipe socket of the high-temperature superheater header of Huadian Weifang Power Plant as an example, it is verified that the ultrasonic phased array detection is feasible in the detection of small diameter pipe welded joints. Finally, the ultrasonic phased array testing process and testing technology of power station boiler small-diameter pipes are summarized, and the development direction of phased array testing application in power plant equipment inspection is prospected.

An ultrasonic signal processing method to improve defect depth estimation in composites based on empirical mode decomposition

In this paper, an ultrasonic signal processing method is proposed to improve depth evaluation of phased array ultrasonic non-destructive testing in composite structures. The proposed algorithm is based on an improved adaptive time–frequency analysis algorithm, and is a combination of empirical mode decomposition, correlation coefficient analysis, a fuzzy entropy algorithm and Hilbert transform. The ultrasonic signal is decomposed into intrinsic mode functions (IMFs) using an improved complete ensemble empirical mode decomposition with adaptive noises. Subsequently, the correlation coefficient and fuzzy entropy are used to select the optimal IMFs to reconstruct the signal. Then, Hilbert transform is executed to obtain the envelope of the reconstructed signal. Finally, the arrival time of the ultrasonic echo is estimated through the signal envelope, and then used to calculate the defect depth. The simulation and experimental results demonstrated that the proposed method has high evaluation accuracy in processing intense noisy signals or overlapped echoes. For simulated signals with different signal-to-noise ratios, the maximum estimation error of arrival time is 0.06 µs. Compared with the traditional gating method, the defect depth evaluation result is significantly improved. In particular, for near-surface defects, the maximum depth detection error is reduced from 0.13 mm to 0.06 mm.

Automated Robotic Systems for Nondestructive Testing of Aerospace Composite Structures

Automated robotic systems are becoming prevalent in many aerospace manufacturing applications, such as laser ablation, sanding, drilling, final assembly, and painting. There are significant advantages to using automated robotic systems for inspection purposes as well: versatility, speed, and repeatability, to name a few. This paper explores using an automated robotic system for the nondestructive testing (NDT) of composite parts. It has a focus on phased array ultrasonic testing (PAUT) but highlights modularity principles in the system that are not coupled to a single inspection method. Because of the articulation inherent in multi-axis robots, inspections of contoured structures become straightforward if the system modules are designed correctly. Examples of such modules, and their advantages when interfaced to an automated robotic system, are included in this paper. It is the author’s intent to show how these system modules might maximize robot capabilities for a broad range of aerospace inspections while keeping a simplistic design that is modular, fast, and straightforward to use. When compared to other aerospace manufacturing processes already using automated robotic systems, the use of robots for NDT seems not only prudent but a favorable goal. This paper offers practical building blocks for achieving this goal.

Nondestructive Characterization of Laser Powder Bed Fusion Components Using High-Frequency Phased Array Ultrasonic Testing

Nondestructive Characterization of Laser Powder Bed Fusion Components Using High-Frequency Phased Array Ultrasonic Testing

Performance comparison of phased array transducers for inspection of dissimilar welds on nuclear reactor components

Trimetallic weld joint of steam generator is crucial and most critical component of Prototype Fast Breeder Reactor (PFBR). Ultrasonic examination of trimetallic welds are more challenging due to the coarse anisotropic grain structure of the weld metal and the mismatch of the acoustic impedance at the weld metal interface, which contributes to increase scattering, sound beam deviation and distortion, reflection and refraction of the incident sound field. This paper presents a comparative study on phased array ultrasonic examination of dissimilar weld joints (P91 – Alloy 800) using linear array (LA) and dual matrix array (DMA) transducer. Prior to the experimental investigations, wave propagation through the dissimilar weld joint and the defect sensitivity is understood by carrying out simulation based on ray-tracing and semi-analytical methods. Weld joint sample with artificial defect such as lack of side wall fusion was fabricated and studied using both transducer of Phased Array Ultrasonic Testing (PAUT).

Resonance Bond Testing: Theory and Application

Resonance bond testing is a nondestructive testing (NDT) technique that is used to detect disbonds, delaminations, and other voids in composite materials. The aerospace industry has seen an increase in the use of carbon fiber reinforced plastics (CFRP) for aircraft and spacecraft construction. Composite materials offer many advantages over traditional metallic structures, which include weight savings, increased strength, design for specific load paths, and the ability to easily construct geometrically complex structures. Resonance bond testing has many established uses for metallic structures as well, such as aluminum skin-to-skin and skin-to-core bonds. This bond testing technique has been around for many decades but is used by only a small portion of the NDT community. Ultrasonic testing (UT), specifically phased array ultrasonic testing (PAUT), using linear array techniques has proven to be a reliable method for the inspection of CFRP laminates. When composite structures do not permit the use of high-frequency sound waves due to rapid attenuation, resonance bond testing is a proven alternative. In this paper, the authors will discuss the theory behind resonance bond testing and how it has and continues to play an important role in the NDT industry.

Phased Array Ultrasonic Testing of Inconel 625 Produced by Selective Laser Melting

Abstract We investigate the use of phased array ultrasonic testing (PAUT) as an offsite non-destructive quality assurance technique for parts made by selective laser melting (SLM). SLM is a popular additive manufacturing (AM) approach for fabricating high-value metallic components with complex geometries. Slight variations in the laser power during fabrication might lead to internal defect development within the part, which could compromise its mechanical strength and fatigue life. PAUT is employed to detect typical internal porosity generated in Inconel 625 samples due to laser power fluctuation during SLM. The typical defect size, shape, and distribution are first identified using metallography and X-ray computed tomography (XCT). B-Scan images of the defect region is then generated experimentally using a 5-MHz linear UT phased array probe. Finite elements simulate wave propagation using geometries obtained from XCT images. The simulation results are compared to the experimental imaging of large defect regions and then used to generate total focusing method images of isolated clusters of 50–200 μm defects. The testing technique illustrates a successful application of PAUT for quality inspection of SLM parts.